Wall and door structure for a sound proof room



Feb. 4, 1964 c. w. LEMMERMAN 3,120,295

WALL AND DOOR STRUCTURE FOR A SOUND PROOF ROOM Filed July 2, 195a v 2 Sheets-Sheet 1 FIG.

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INVENTOR. CARL W LEM/WERMA/V ATTORNEYS WALL AND DOOR STRUCTURE FOR A SOUND PROOF ROOM Filed July 2, 1958 Feb. 4, 1964 c. w. LEMMERMAN 2 Sheets-Sheet 2 z 1. allinlll Th IN V EN TOR.

CAPL W LEM/ IEPMA/V TTOR/VE Y5 RQ m R nited States Patent 3,12ii,25 WALL AND DUUR STRUtCTURE EFGR A SQUND PRQQF HUGE/i Carl W. Lemmerman, West Hfitford, (Conn. C. W. Lerninerrnan, Ina, ill Lafayette St, Hartford, Conn.) Filed .luly Z, 1953, Ser. No. 746,250 2 Ciairns. (Cl. 189-45) This invention relates generally to sound isolating enclosures, and more particularly, to a novel and improved sound confining enclosure for use during aircraft engine testing.

The very high noise level resulting from aircraft engines under test, and particularly from jet engines, has resulted in the provision in test facilities of sound isolating engine enclosures for the protection of servicing personnel.

A major object of the present invention is to provide such a sound isolating structure of improved construction and effectiveness; which confines a major portion of the engine noise to the area of the enclosure, hence reduces the ambient noise to an acceptable level, and which is particularly effective as a sound barrier throughout the range of noise frequencies attendant jet engine operation.

Another object is to provide improved sound attenuating panels which may be easily fabricated, are relatively light in weight, and which may be quite easily interlocked to form the walls of an enclosure, thus permitting relatively simple assembly and subsequent reassembly of the enclosure when it becomes desirable to move its location at the test facility.

Other objects will be in part obvious and in part pointed out more in detail hereinafter.

The invention accordingly consists in the features of construction, combination of elements and arrangement of parts which will be exemplified in the construction hereinafter set forth and the scope of the application which will be indicated in the appended claims.

In the drawings:

FIG. 1 is a fragmentary front view of a noise confining chamber constructed of multiple sound insulating panels, with a noise insulating door positioned in one of the panels, with a door sill closure structure shown dotted;

FIG. 2 is a sectional view taken substantially along the lines 22 of FIG. 1 showing the panel construction and a sound insulating seam joining aligned panels;

FIG. 3 is a horizontal sectional view taken substantially along lines 33 of FIG. 1 showing a preferred construction of the door, in closed position; and

FIG. 4 is a vertical sectional view taken substantially along lines 4- 1 of FIG. 1 showing a fluid operable closing apparatus associated with the door sill.

PEG. 1 illustrates one side wall and the top and bottom enclosures of a sound isolating chamber, the side wall, generally designated Zii, being constructed of pre-fabricated sound attenuating panels 22, 24, and 26, aligned and bolted together as later described. The panels as shown are supported on a concrete floor and a suitable top wall, shown dotted at 1'7, may comprise either like panels or alternately the upper margin 16 of the side wall panels may abut a concrete or other ceiling surface forming part of the room in which the enclosure is assembled.

The panels are relatively light in weight compared to the concrete and steel panels heretofore commonly used in the construction of sound isolating enclosures. The present invention resides in the panel wall construction, the manner in which the panels are joined to form a wall, and in the construction of a door 23 which is shown hung in a doorway in panel 24 by hinges 3 3 from which extend hinge bars 34 transversely of the door. The inventive features are also incorporated in the manner in which the door is sound insulated in respect to the doorway along the jambs and header as Well as along the bottom margin or sill of the door. Door 28 may be opened by pull handle 32, and a latching mechanism 36 including an operating handle 38 bolts the door in place in a manner later described.

FIGS. 2 and 3 show similar wall constructions in that both walls include a sound blocking panel positioned out- Wardly of a sound absorbing panel in respect to the enclosure formed by the Walls, and later described in detail. FIG. 3 illustrates the internal construction of both a wall panel and a door panel as well as the marginal configuration of the door and its mating relation to vertical margins r jambs of the doorway to provide a sound insulating seal therebetween when the door is in a closed position. The sound absorbing panel 66 of FIG. 2 includes the structure between an outer steel plate 62 and an inner steel plate 63, while the sound absorbing panel 61 includes the structure thereabove as viewed. A floating septum 64 provides a partition substantially midway between the outer and inner plates of panel to divide the space therebetween into two compartments and 66 which are filled with a suitable sound absorbing material 67.

FIG. 2 shows the left edge of a sound blocking panel 61} interlocked with the right edge of an aligned sound blocking panel 66', panels so and 6%? being of uniform construction. The opposite edges of panels 60 and 6%, not shown, are identical to the corresponding edges shown with the interlocking therebetween being identical to that herein described. The left edge 74 of compartment 65, formed by marginally channeling plate 63, is positioned in staggered relation to the left edge 71 of compartment 66 formed by the margin of plate 62 with the edges and '71 in the same staggered relation as are the right hand edges 72 and 73 respectively of compartments 65 and d6 of the dual compartment sound blocking panel 6% at the left side of HS. 2. Since edges 72 and 73 of panel 6% correspond to the right edges of panel 6%, cornpartments 65 and 66 are of like horizontal dimension with the left edge 70 of compartment 65 offset to the left of edge 71 of compartment 66. Right edge '72 of compartment 65 is ofl-set to the left of right edge 73 of that compartment, hence compartments 6% are horizontally offset from compartment throughout the wall formed by the panels and the right edge of the adjacent sound blocking panels such as dd" mates with the left edge of a similar adjacent panel such as 61 and in that manner the panels are bolted together to provide a unitary wall construction.

Floating septum 64 is resiliently supported in panel 6t) by structure at the panel margins and adjacent the brackets which bolt the panels together. As shown in FIG. 2, angle bracket 75 is fixed to the left edge of outer plate 62 of panel 6i and angle bracket 76 is secured to the right edge of corresponding outer plate 62 adjacent edge '73 of panel as. Rubber strips 77 form resilient spacers between end Walls 7% land 72 and end walls '74) and 73 while thinner rubber spacers '78 are maintained clamped 1 etween the anchor brackets '75 and '76 by bolts 8!) to thus maintain the ends of the panels in clamped engagement with their resilient spacers with the spacers under compression. A stud 81 extends outwardly from a retainer 84 in compartment 65 which retains the stud head 83 with Lhe shank of the stud extending through compartment 66 to be maintained clamped by nut 82 to the base of the bracket 76 and the margins of retainer 84 clamped against flange 85 of the channel forming end wall 7?, flange 85 extending from end wall 70 a distance equal to flange 86 secured to end wall 71 in parallel spaced relation to flange 85 to form a channel therebetween for a resilient mount or septum isolator 88 which is centrally channeled to receive and resiliently mount a margin of the rigid steel floating septum 64. The right edge of sound locking panel as is likewise provided with a septum isolator 88 mounted between flanges 85 and as for a like purpose, isolator 88 preferably being of neoprene or similar rubber.

Floating septum 641 has secured to each side thereof a plurality of channel bar stilr'eners gt), V-shaped in cross section, and positioned in parallel spaced relation, with each alternate stiffener on the opposite side of the plate. The spacing between the stiifeners is selected as a definite function of the sound frequencies to be blocked. While sound blocking panels such as so may be maintained clamped in unitary assembly as above to form a wall such as shown in H6. 1, it may be desirable under certain circumstances additionally to provide a sound absorbing panel 61 adjacent the inner wall surface of the sound blocking panels. Such a sound absorbing panel consists of perforate steel plates 91 and 92 maintained in parallel relation by spacers 93, FIG. 3, with plate 92 contiguous to inner plate 63' of the first mentioned panels and the space between plates 91 and 92 filled with a suitable sound absorbing material. A wire mesh 94 may be positioned adjacent plates 9d, if required, to constrain the sound absorbing material from working out of the plate perforations.

It is apparent from the above description that the sound abating or isolating enclosure in which the inventive principles are incorporated consists of relatively light weight panels and a door of similar construction which are prefabricated prior to final assembly and which may be easily assembled at a test facility at any convenient location within a building or in fact outside the building if desired. Measurements of the sound level outside enclosures constructed in accordance with the invention conclusively prove that such panels constructed of an overall thickness of 6 inches, which includes both the sound blocking and sound absorbing panel, are equal as sound barriers to a concrete panel of 12. inches total thickness. Sound isolating compartments of the concrete panel type are normally of permanent construction and must be demolished rather than disassembled when no longer useful at a particular location. While a sound isolating enclosure constructed in accordance with the invention cannot be termed portable in the normal sense of the word, such an enclosure may be disassembled and reassembled at a new location within a matter of hours, hence substantial cost savings are effected with comparable savings in down time, since several days rather than hours are required to construct a concrete enclosure.

While the invention is not to be limited by any particular theory of operation, it is believed that the effectiveness of the sound blocking panel over previous structures employing compartments filled with sound insulating material is as follows. The sound from a source such as a jet engine includes many frequencies, some of which are absorbed by the inner sound absorbing panel when employed inwardly of the sound blocking panel, it being understood that the use of an inner sound absorbing panel is optional, its use depending on the magnitude of sound to be abated. Under some conditions the wall may cornprise only a sound blocking panel. The mixed frequency sound waves conveyed through air to arrive at the inner wall 63 of the sound blocking panel, whether after passing through the sound absorbing panel or not, causes panel 63 to vibrate at one of the relatively audible sound frequencies and possibly at several harmonics thereof beyond the (audible range. The sound which causes the fundamental vibration of plate as is to a large extent absorbed by the insulating material ltill disposed between plate 63 and the septum plate 64. Sound of substantially higher frequencies from the source pass directly through plate as without affecting its fundamental frequency of vibration, it being well known that steel is an excellent medium for sound transmission, and that there exists no interference between sound waves of various frequencies, regardless of the medium through which sound travels in longiq tudinal or compression waves. While plate 63 is thus vibrating at a relatively low frequency and dissipating sound energy into the adjacent insulating material, the higher frequency sound arrives at septum plate d4 without substantial attenuation.

Septum plate 64, being float-ably mounted marginally thereof and provided with transverse stiffeners W- which function somewhat as frets on a musical instrument, is capable of vibrating as a unit at a relatively low sound frequency, but portions thereof intermediate the stilfeners vibrate at much higher frequencies than does plate 64 as a unit. The resilient isolators promote the unitary low and the section alized high vibrations and the high frequencies which pass through plate 63 vibrate the areas between the septum stiffeners. The natural period of vibration of the isolated areas is an upper harmonic of the high frequencies which cause them to vibrate, hence they serve as frequency convertors to remove some of the sound energy from the audible range. The insulating material on each side of the septum plate is loosely packed, hence neither the vibration of the plate as a whole or the higher vibration of the isolated areas thereof is substantially damped by that material. The stiffeners or frets 9d are mounted in parallel spaced relation at distances selected in view of the high frequency sound to be abated. The septum portions intermediate the frets thus serving to convert substantial sound energy into frequencies which are above those audible to the human ear, effectively eliminate a large portion of the sound energy as an acoustical nuisance. Since the septum plate vibrates as a unit at a relatively low frequency, the sound energy of that frequency is dissipated by energy conversion into the insulating material on each side of the septum plate. The outermost insulating material receives most of that energy, along with some of the energy which was not dissipated by the innermost layer of insulating material as a result of the transfer thereto by plate 63.

The outer wall 62 is also vibrated by those sound waves which travel through the panel structure, but the vibration of that wall is substantially less than either wall 63 or septum 64, due to attenuation through the panel. The panel structure thus promotes dissipation of audible sound by both resonator absorption with the walls serving as a sound filter; by viscous forces which degrade the sound energy into heat; by thermal conduction and radiation; and by frequency conversion. The septum divides the space between the walls 62 and 63 into a pair of parallel sound traps which promote such dissipation in a known manner. Thus the panel simultaneously employs several effective methods of attenuation and a blending of the low level escaping sound into complex frequency patterns which are accoustically unobjectionable to persons in the immediate area surrounding the enclosure.

The construction of the door shown in FIG. 3 is quite similar to the panel construction of FIG. 2 except that single panels are employed which terminate at each side of the door and there is no need for interconnecting panels in the staggered relation above described. Numbers and lull in FIG. 3 identify compartments which are equivalent to compartments 65 and do of the FIG. 2 structure, and the floating septum 64 is identical to the septum given the same numeral in FIG. 2 which is also true of the stiffeners fit isolators 88 and the inner and outer plates as and 62.

3 shows the wall panels terminating in end wall portions 79 and 'il which support isolator mounting brackets as for isolators 8? corresponding to like structure in FIG. 2. The door panel has opposite end wall portions 72 and 7'3 with brackets $6 and isolators 8d mounting floating septum 64 in the same manner as in the side wall panels. In FIG. 3 wherein the sound absorbing panel 96 and the sound blocking panel 5E7 are combined as a. unit in the door, end portions 1% and 1&5 conform to the contour of the doorway at each side of the panel. Each door margin includes a perforate portion 106 terminating in a plane with the perforate inner plate of the sound absorbing panel 96 at one end and in a plane with the irnperforated outer portion of the sound blocking panel d7 at the other end. The Z-s'haped portion terminates in a channel portion 107, the end wall of which engages panel plate 63. The opposite end of the Z forms an enclosure with outer angle portion 168 to complete the door margin contour. Both angle plates 107 and 108 are imperforate, with the structure at each side of the door being of similar construction.

Sound absorbing panel as is secured against sound blocking panel 97 by jumper strips 11% between inner plate 91 and channel strips m7. Channel strips 108 are secured to the end walls 72 and 73 of panel 97. Portions M2 and 114 of adjacent sound absorbing panels are aligned with the sound absorbing door panel as. Panel 96 has end channels 93 inwardly of the door margins. The door and the wall panels defining the jambs are thus mated in a manner to provide a sound absorbing junction or seam therebetween, Z shaped in cross section, with the facings along the Z of perforate metal sheet stock.

The Z-shaped portion 115 facing door portion 106 is secured to the panel outer plate 62 while the opposite vertical edge of the Z-shaped portion 115 merges with the wall angle portion 116 having the free end thereof bent inwardly. A compartment channel 118 has one end secured to and intermediate the vertical edges of the Z- shaped portions 115, the other end being secured to a bracket 119. Brackets 119 and 120 form a rectangular compartment 121. Portions 116 and 118 of the door j amb complete the compartmentalized structure. Jumper strip 122 ties bracket 120 tothe adjacent sound absorbing wall panel. Thus the structure described forms compartments 1'21, 125, and 126 in both panel portions 112 and 114, those compartments being filled with suitable sound absorbing material, as are the mating compartments at each side of the door. The juncture above described as extending along each side of the door also extends along the top of the door. A special closure apparatus, later described, provides a sound seal along the door sill.

The door locking control mechanism, operable by handles 38, 3%, through toggle plate 41 and stud 40 permits the door to be bolted from either side. Handle pivoting causes toggle plate 41 to actuate bolt 42 which is pivotally connected through link 23 to plate 44 mounted on pivot pin 45 to the door. The outer end of bolt 42 engages a keeper 46 secured to panel Zil', keeper 46 being associated with a pneumatic or hydraulic control valve 43 as shown in FIG. 4. Lower bolt 4 2 is shown directly connected with the control valve 48, and with door 28 fully closed and handle 38 moved to its closed position as shown, bolt 42 engages an operating lever in control valve 48 to actuate a conventional pneumatic or hydraulic cylinder Stl having a piston actuated rod 140' which in turn operates the movable sound sealing dam S2 of a threshold assembly 54. The threshold assembly, FIGS. 1 and 4, includes a flanged metal well 13% set in a firm foundation 131, such as concrete. The flanges of the well are disposed below the top surface 132, at the floor level of the sound isolating enclosure. Elongated strips 133 are secured to the flanges by bolts 134, with each of said strips 133 resting on a metal stop strip 13% which acts as a limiting means for upward movement of a plunger.

Cylinder 59 is fixed by bolts 139 to the bottom of the well. Piston rod ll iti carries a plate 141 for the support for spaced channel members 142 and a threshold closure plate 52 mounted thereon. Plate 52 is positioned flush with strips 133 and floor 132 when piston 14d is retracted, to permit the door to swing. Rubber buffer strips 144, fixed to piston plate Ml, provide cushioning during the upward piston stroke by engaging the stop strips 135 as plate 52 moves into contact with lower edge 148 of the door to close the sill space therebelow.

With either door handle moved to its closed position, bolts 42 engage their respective keepers 46, the lower keeper being associated with the control valve unit 48 for actuation to permit fluid flow to the valve from the pressure source, through conduit 3.46 to cylinder 50 to raise rod 14% and threshold plate 52 upwardly for plate engagement with the bottom edge 148 of the door. The fluid pressure remains on to hold the engagement until intentionally released by known means, not shown, for retraction of the plate to its recessed position.

An overhead sound insulating panel similar to that shown in FIGS. 1, 2, and 3 may be employed as a ceiling and secured to the side wall construction of the enclosure in a manner which will be readily suggested from the above description. Paneling may also be provided on the bottom or floor of the enclosure, particularly if the sound abatement chamber is to be used on shipboard or in a building above ground level.

The sound absorbing panel preferably has sound absorbing materials such as glass wool between the panel plates for heat absorption and attenuation by viscous forces of the sound energy at various frequencies. The compartments of the sound blocking panel preferably also have similar sound attenuation material therein, but the floating septum arrangement may under certain conditions be employed without such material in the compartments. The perforate structure defining the Z shaped door seal promotes sound energy attenuation in accordance with principles well understood in the art.

There has thus been provided a noise attenuator of novel and improved construction, particularly adapted for use with jet engine aircraft to reduce the noise level thereof during surface-borne testing of the engine. The attenuator effectively reduces the level of both the low and high frequency exhaust noises without the use of large and weighty structures normally associated with effective attenuation. An attenuator constructed in accordance with the invention is not, however, limited to use as a prefabricated attenuator which may easily be disassembled, inasmuch as the inventive concepts are equally suited for incorporation in fixed test cells not adapted for disassembly and reassembly.

As will be apparent to persons skilled in the art, various modifications and adaptations of the structure above described will become readily apparent without departure from the spirit and scope of the invention, the scope of which is defined in the appended claims.

I claim:

1. In a sound isolating structure comprising a stationary enclosure including sound attenuating walls formed of sheet metal, one panel being provided with an opening, a sheet metal sound attenuating closure for said opening,

eans mounting said closure for hinged movement between positions opening and closing said opening, the wall margin defining said opening and the margin of said closure being contoured to mate in a plurality of planes arranged in generally 2 configuration, a closed comp-artment formed in the wall and in the closure and including the mating wall and closure margins as wall portions thereof, the sheet metal forming said mating contours being perforated throughout and sound attenuating material in said door and said wall adjacent the perforations in the margins.

2. A sound isolating structure comprising a plurality of sound attenuating walls, each said wall having marginal edges, means mounting at least a portion of one wall for movement relative to the adjacent wall, the movable wall portion having at least one marginal edge terminating in a plurality of planar surfaces, the adjacent wall terminating in mating planar surfaces for cooperation with the confronting marginal edge of the movable wall portion to define a tortuous sound path therebetween, the confronting edges of the wall and movable portion being part of respective closed compartments formed at the margins thereof and extending throughout the tortouous sound path, the planar surfaces of the confronting edges of the movable wall portion and adjacent wall References Citefi in the file of this patent UNITED STATES PATENTS 725,052 Dillon Sept. 27, 1962 1,231,069 Schaffert June 26, 1915 2,276,788 Norris Mar. 17, 1942 8 Plarkes Aug. 17, 1948 Moten Nov. 20*, 19 51 Bollinger Feb. 12, 1952 Bagnard May 29, 1956 Bragman Dec. 211, 1957 Thomson Aug. 26, 1958 Kod-aras Jan. 26, 1960 Haul": Mar. 8, 1960 

1. IN A SOUND ISOLATING STRUCTURE COMPRISING A STATIONARY ENCLOSURE INCLUDING SOUND ATTENUATING WALLS FORMED OF SHEET METAL, ONE PANEL BEING PROVIDED WITH AN OPENING, A SHEET METAL SOUND ATTENUATING CLOSURE FOR SAID OPENING, MEANS MOUNTING SAID CLOSURE FOR HINGED MOVEMENT BETWEEN POSITIONS OPENING AND CLOSING SAID OPENING, THE WALL MARGIN DEFINING SAID OPENING AND THE MARGIN OF SAID CLOSURE BEING CONTOURED TO MATE IN A PLURALITY OF PLANES ARRANGED IN GENERALLY Z CONFIGURATION, A CLOSED COMPARTMENT FORMED IN THE WALL AND IN THE CLOSURE AND INCLUDING THE MATING WALL AND CLOSURE MARGINS AS WALL PORTIONS THEREOF, THE SHEET METAL FORMING SAID MATING CONTOURS BEING PERFORATED THROUGHOUT AND SOUND ATTENUATING MATERIAL IN SAID DOOR AND SAID WALL ADJACENT THE PERFORATIONS IN THE MARGINS. 